Comment: According to is always a preposition. It is called a complex preposition because it has two words, not because it is difficult or complicated. Common meanings include: 1) in conformity, 2) naming the source of the statement - According to experts, 3) depending on - According to the circumstances, he could be helpful.

From each according to his ability, to each according to his work. (principle of socialism -- adjusted Marxian principle to recognize that people don't work when it isn't necessary)